1. Field of the Disclosure
The present disclosure relates to compositions and methods of use of cashew nut shell liquid (CNSL) and its derivatives as one of the components for decreasing the viscosity of heavy oils, extra heavy oils, high asphaltene natural bitumen, and tar sands, thereby increasing the ability of the resulting mixture to be piped, transported, stored and used.
2. Description of the Related Art
The heavy oil resource is vast. The estimated volume of technically recoverable heavy oil (434 billion barrels) and natural bitumen (651 billion barrels) in known accumulations is about equal to the Earth's remaining conventional (light) oil reserves. USGS estimates the total resource of heavy oil in known accumulations is 3,396 billion barrels of original oil in place and the total natural bitumen resource is 5,505 billion barrels of original oil in place. Despite abundance of its resource, it remains largely unexploited because of difficulties associated with its recovery, transportation and refining.
Heavy oil is viscous because of the high bitumen/asphaltene content which tends to form aggregates that impede pumpability or flowability of crude oils. The viscosity of heavy oil can be up to a million times more viscous than water. The problem of transporting heavy oil, especially over long distances (>150 km) is acute and the only practical solution currently available is to add a diluent or cutter, such as light petroleum distillates, heat or both to reduce viscosity and enable the flowability for transportation of these materials. Large quantities of heavy oil have been identified worldwide, however economic recovery of these heavy oils is most challenging, particularly with respect to energy required to extract and upgrade oils and the depths at which much of this resource is located.
The disadvantages associated with using solely petroleum-based solvents, diluents or dispersants, to reduce the viscosity of residual fuel oils, heavy oils and tar sands include that they are costly as well as hazardous to transport and handle due to their volatility and combustibility. Management and handling of highly volatile, low flash point and combustible petroleum-based products is also challenging because volatilization losses result in increased environmental and health and safety-related risks, pollution control costs and regulatory requirements. Cutter stock and petroleum distillates that are commonly used as diluents to reduce the viscosity of residual fuel oils, heavy oils and tar sands are paraffinic and known to destabilize suspended asphaltenes in residual fuel oils, heavy oils and tar sands. Destabilization of asphaltenes by paraffin solvents can result in precipitation and subsequent asphaltene sludge accumulations in oil transportation and storage systems, including valves, pumps, pipes and large storage vessels. The presence of asphaltene sludge accumulation in oil transportation and storage systems, including valves, pumps, pipes and large storage vessels creates serious operational problems in their effective and efficient operation resulting in costly repair and maintenance costs.
No. 5 and No. 6 Fuel Oil are defined as residual fuel oils (RFOs) or heavy fuel oils by the American Society for Testing and Materials (ASTM) and are what remains after distillate fuels are removed from crude oil during the refining process. No. 6 Fuel Oil is also referred to as Bunker C oil. No. 6 fuel oil including Bunker C fuel oil is generally used for the production of electric power, space heating, vessel bunkering, and various industrial purposes. No. 6 may contain No. 2 fuel oil to get it to meet specifications. No. 5 fuel oil is a mixture of No. 6 (about 75-80%) with No. 2.
Asphaltenes are polar molecules that stay in suspension in oils because of their outer molecular structure. During thermal cracking in petroleum refineries, the outer molecular structure is modified. If the structure is greatly affected, asphaltenes will become unstable and precipitate forming a sludge. Blending stable petroleum distillates (cutter stock) with residual oil fractions can also affect the stability of the asphaltenic compounds. Cutter stock and gas oil are petroleum distillate derivatives used in blending to reduce the viscosity of heavier residual fuel oils to meet specifications for use to make residual fuel oils and No. 6/Bunker C oil. Because asphaltenes are kept in suspension in heavy oils by the presence of aromatic compounds, when low aromatic content cutter stocks are used to decrease the viscosity of heavy oils, the aromatic content of the oil can become so low that asphaltene precipitation takes place.
Group V oils are defined as oil having an API gravity less than 10 at 60° F. Group V oils include very heavy residual fuel oils, asphalt products, and very heavy crude oils. Public utilities that use residual oils to generate electricity have started to evaluate the use of Group V fuel oils because of their lower costs and higher BTU values. The utility industry refers to these Group V Residual Fuel Oils (GPVRFO) as LAPIO (Low API Oil). GPVRFO are at the lower API gravity end of conventional No. 6 fuel oils. Typically, GPVRFO contain a greater fraction of heavier components than typical No. 6 fuel oils. The production of GPVRFO can include the heavy residues from several refining operations that are typically blended with lighter distillates and by-products. The goal of GPVRFO blending is to meet specifications of viscosity, pour point and sulfur defined by the end user. Incompatibility with various cutter stocks leading to asphaltene precipitation during transport and storage can be a significant problem with GPVRFO products. The use of higher flash point low aromatic content distillate to lower the viscosity of No. 6 and Group V oils can result in flash points being too low with respect to specifications.
Thus, there is a need for a safer, renewable, cost effective, green viscosity reducing agent for extraction of oils as well as the processing and transport of heavy and extra-heavy crude oils, residual fuel oils, and tar sands.